Researchers from the University of Zaragoza (Aragosaurus-IUCA group), the University of the Basque Country and the Nova University of Lisbon have defined a new species very primitive of sirenian (marine mammal) in the UNESCO World Geopark of Sobrarbe-Pirineos, Huesca.

The importance of the discovery is that it is the first quadruped siren of Eurasia and the oldest species in western Europe with 42 million years.

The results of this scientific work encourage us to continue in the line of support for the research we have been doing since the Sobrarbe-Pirineos Geopark through our Research Aid program, which has not only partially financed the work presented here but also At present, it also finances the location of new deposits that will help to increase the paleontological knowledge of the Eocene in the Pyrenees and that will allow the valorization of these deposits in terms of geological heritage.

The sirenians are the only herbivorous marine mammals, hence they are also known as “marine cows”. They are currently represented by dugongs and manatees that inhabit rivers and coasts of tropical latitudes.

The new species of sea cow found in the UNESCO World Geopark of Sobrarbe-Pirineos has just been published in the prestigious scientific journal “Scientific Reports” by the authors Ester Díaz Berenguer, José Ignacio Canudo (University of Zaragoza), Ainara Badiola (UPV/EHU) and Miguel Moreno Azanza (Nova University of Lisbon). The chosen name is “Sobrarbesiren cardieli”, in honor of the region of Sobrarbe and Jesús Cardiel Lalueza, discoverer of the site.

Sirenian skull Sobrarbesiren Cardieli

It is a key fossil to know the evolution of the sirenians, since it was a quadruped animal, with functional hind limbs and was not fully adapted to aquatic life. The investigations are being carried out in the context of the doctoral thesis of Ester Díaz Berenguer, who is currently studying the skeleton of this sirenio in depth in order to know its appearance and find out if it was capable of supporting its weight or, for otherwise, they were only used for swimming.

The paleontological excavations at the Castejón de Sobrarbe deposit started in 2009 under the direction of Dr. Ainara Badiola and since then more than 600 fossils of vertebrates of Middle Eocene age (approximately 42 million years) have been recovered. Of them, some 300 fossils are from Sobrarbesiren, of at least six different individuals between adults and juveniles. The new Sirenio Sobrarbesiren is represented by almost all bones of the skeleton of the animal; They have recovered three skulls, numerous vertebrae and ribs and bones of the fore and hind limbs. Among them, two pelvises, a femur and the oldest sirenian fibula in the world stand out. In the same deposit, remains of turtles, crocodiles, lizards, sharks and small mammals have also been recovered, as well as fossils of invertebrates and plants that together with geology allow us to reconstruct the environment where Sobrarbesiren lived. It would be a coastal area of a gulf open to the Cantabrian Sea, where a delta with a lot of vegetation and a tropical climate would end.

Ribs of Sobrarbesiren Cardieli

The good conservation and abundance of fossils makes the Sirenians of Sobrarbe the best collection of this group of the Middle Eocene of the world. Their interest increases even more if we consider that Sobrarbesiren is the first quadruped siren of Eurasia and the oldest in Western Europe. This discovery will place Spain, and especially the province of Huesca, as one of the key points of the world in the study of the initial evolution of marine mammals.

The fossils have been excavated with the permission of the Directorate General of Culture and Heritage of the Diputación General de Aragón (DGA) and are deposited in the Museum of Natural Sciences of the University of Zaragoza. Soon the most unique pieces can be seen in the permanent exhibition of the Museum located in the Paraninfo building of the University. The investigations that have been carried out and those that are in progress have the support and subsidies of several institutions (Universities of Zaragoza and the Basque Country, UNESCO World Geopark of Sobrarbe-Pirineos, Governments of Aragon and the Basque Country, Mineco and the European Fund of Regional Development).

Represented today by only four species, this group of mammals first appeared 50 million years ago. They evolved from terrestrial mammals in the African continent. Adaptation to the aquatic life of the sirenios led to a series of bodily changes, such as the loss of hair and ears, the development of a body more hydrodynamic, with the neck shortened, forelimbs modified in fins and hind limbs that were disappearing until they were reduced to a vestigial pelvis and femur. On the other hand, they developed elongated lungs that span almost the entire length of the animal’s body. This, together with a flattened tail, which helps them propel themselves in the water, and the development of very thick and dense bones, has allowed them to transform themselves into slow swimmers who feed on shallow seagrass beds.